A power distribution system is generally made up of a high-voltage system (normally 6600 V) and a low-voltage system (for example, 100 V to 200 V). Power-receiving terminations used by general consumers are connected to the low-voltage system. Power utilities are obligated to maintain the voltage at the power-receiving terminations used by general consumers within an appropriate range (for example, between 95 V and 107 V in the case of a receiving power of 100 V). Therefore, power utilities adjust the amount of control (for example, operate a tap) of a voltage control apparatus (such as an LRT (Load Ratio Control Transformer: on-load tap-changer transformer) or an SVR (Step Voltage Regulator)) connected to the high-voltage system in order to maintain the voltage at the power-receiving terminations used by general consumers. In the following descriptions, a power distribution system indicates a high-voltage system thereof unless otherwise specified.
Photovoltaic systems of various sizes, such as residential photovoltaic systems and mega solar systems, have recently been connected to power distribution systems and thus it is becoming essential when operating the systems to know the amount of photovoltaic power generation carried along each power distribution line (or each power distribution section). It is possible to estimate the amount of photovoltaic power generation carried along each power distribution line on the basis of the amount of photovoltaic power generation measured at a plurality of points in the power distribution line or the amount of solar radiation measured for each power distribution line. These methods, however, necessitate installation and management of measurement equipment and communication equipment. Moreover, it is considered imperative to know approximate voltages of the power distribution lines in order to maintain the power distribution system at an appropriate voltage. Thus, there is a plan to dispose sensors near the delivery points and the terminations of the power distribution lines and measure the voltage, current, active power, inactive power, and the like.
A method is disclosed in Patent Literature 1 below of measuring the active power and inactive power upstream of a photovoltaic device and estimating the photovoltaic power generation output by using independent component analysis.